diff --git a/phosphor-regulators/src/rule.hpp b/phosphor-regulators/src/rule.hpp
index 25be1e9..3fb21a6 100644
--- a/phosphor-regulators/src/rule.hpp
+++ b/phosphor-regulators/src/rule.hpp
@@ -52,7 +52,7 @@
      *
      * @param id unique rule ID
      */
-    Rule(const std::string& id) : id{id}
+    explicit Rule(const std::string& id) : id{id}
     {
     }